A problem has been disclosed in previously filed applications (such as application Ser. No. 582,838) of this Applicant which problem is directed to the removal of metals in pickle liquors and the like. A pickle liquor is generally described as the acid bath used at a galvanizing plant or the like which acid when freshly charged has a pH of 1 and no metal therein and after use, the pH is raised perhaps slightly, and a noticable amount of metal in solution prevents its further use. Heretofore, the acid bath has been dumped. This creates a very difficult pollution problem. As disclosed heretofore, an apparatus has been provided which removes the metal content of the pickle liquor. This has utilized, in the main, a tank divided by an ion-permeable acid proof polypropylene diaphragm with an anode and cathode on opposite sides of the diaphragm. Typically, one of the electrodes has been formed of carbon and the other has been made of aluminum. The metals in the acid solution are deposited onto the cathode and are recovered.
This apparatus has proven quite successful. It is desirable to provide a pretreatment apparatus in accordance with the teachings of the present invention which is configured quite differently from the planar acid proof diaphragm, large plate electrodes and substantial tank disclosed in the copending application.
The apparatus of the present invention enables practically all of the free mineral acid to be recovered in pretreatment. Pretreatment apparatus contemplated by the present invention is easily constructed and moreover, is configured quite differently to enable it to be installed as an intermediate or pretreatment recovery apparatus in the process of purifying spent pickle liquor to enable its subsequent reuse.
This disclosure in particular avoids some of the mechanical limitations of the previous disclosures. They are directed to the planar membrane, parallel metal electrodes for metallic extraction and large tank which are so typical of permanent installations for large scale plants. The apparatus disclosed herein is intended to be used differently for extraction of free mineral acid ions and thereby lends flexibility to the plants of the previous disclosures. It permits a deviation in equipment geometry which is far more convenient to work with in some circumstances. Moreover, the equipment disclosed herein functions in the same manner and hence lends flexibility to the user of this equipment.